Hi, I recently upgraded ffmpeg and suddenly started to get errors when decoding Matroska files. My colleague Yujing Huang discovered this when making a H264 file from a FFV1/MKV 57 second file, and a single frame was duplicated from 26 seconds to 48 seconds. When decoding the file with -f null - , we got this error: [matroska,webm @ 0x7fcf3a80b000] Element at 0x32c212a ending at 0x32c68b1 exceeds containing master element ending at 0x32c2123 I am able to replicate the issue with git-master creating a file like this: $ ./ffmpeg -f lavfi -i testsrc -t 1 1sec.mkv ffmpeg version N-94168-g0f39ef4db2 Copyright (c) 2000-2019 the FFmpeg developers built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn) configuration: libavutil 56. 30.100 / 56. 30.100 libavcodec 58. 53.101 / 58. 53.101 libavformat 58. 28.101 / 58. 28.101 libavdevice 58. 7.100 / 58. 7.100 libavfilter 7. 56.100 / 7. 56.100 libswscale 5. 4.101 / 5. 4.101 libswresample 3. 4.100 / 3. 4.100 Input #0, lavfi, from 'testsrc': Duration: N/A, start: 0.000000, bitrate: N/A Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 320x240 [SAR 1:1 DAR 4:3], 25 tbr, 25 tbn, 25 tbc File '1sec.mkv' already exists. Overwrite ? [y/N] y Stream mapping: Stream #0:0 -> #0:0 (rawvideo (native) -> mpeg4 (native)) Press [q] to stop, [?] for help [mpeg4 @ 0x7fdab3002a00] too many threads/slices (16), reducing to 15 Output #0, matroska, to '1sec.mkv': Metadata: encoder : Lavf58.28.101 Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 25 fps, 1k tbn, 25 tbc Metadata: encoder : Lavc58.53.101 mpeg4 Side data: cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1 frame= 25 fps=0.0 q=1.6 Lsize= 49kB time=00:00:00.96 bitrate= 419.5kbits/s speed=21.7x video:48kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.987251% and decoding it with $ ./ffmpeg -i 1sec.mkv -f null - ffmpeg version N-94168-g0f39ef4db2 Copyright (c) 2000-2019 the FFmpeg developers built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn) configuration: libavutil 56. 30.100 / 56. 30.100 libavcodec 58. 53.101 / 58. 53.101 libavformat 58. 28.101 / 58. 28.101 libavdevice 58. 7.100 / 58. 7.100 libavfilter 7. 56.100 / 7. 56.100 libswscale 5. 4.101 / 5. 4.101 libswresample 3. 4.100 / 3. 4.100 Input #0, matroska,webm, from '1sec.mkv': Metadata: ENCODER : Lavf58.28.101 Duration: 00:00:01.00, start: 0.000000, bitrate: 403 kb/s Stream #0:0: Video: mpeg4 (Simple Profile), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 25 fps, 25 tbr, 1k tbn, 25 tbc (default) Metadata: ENCODER : Lavc58.53.101 mpeg4 DURATION : 00:00:01.000000000 Stream mapping: Stream #0:0 -> #0:0 (mpeg4 (native) -> wrapped_avframe (native)) Press [q] to stop, [?] for help Output #0, null, to 'pipe:': Metadata: encoder : Lavf58.28.101 Stream #0:0: Video: wrapped_avframe, yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc (default) Metadata: DURATION : 00:00:01.000000000 encoder : Lavc58.53.101 wrapped_avframe [matroska,webm @ 0x7ff200805200] Element at 0xc4a2 ending at 0xc4dd exceeds containing master element ending at 0xc49d frame= 25 fps=0.0 q=-0.0 Lsize=N/A time=00:00:01.00 bitrate=N/A speed= 84x video:13kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown Best, Kieran O'Leary Irish Film Institute ------ This email has been scanned for spam and malware by The Email Laundry.